This relates generally to resistive random access memories (ReRAMs).
ReRAM relies on materials that can be electrically switched between a higher conductive state and a lower conductive state several times. One type of ReRAM, a phase change memory, uses phase change materials, i.e., materials that may be electrically switched between a generally amorphous and a generally crystalline state. One type of phase change memory element utilizes a phase change material that may be, in one application, electrically switched between a structural state of generally amorphous and generally crystalline local order or between different detectable states of local order across the entire spectrum between completely amorphous and completely crystalline states.
One time programmable fuses may be used in conjunction with a phase change memory array. For example, fuses may be programmed permanently to store information which should not be changed. This information may include trimming values set during manufacture, microcode, and redundancy addresses to replace defective memory elements with replacement memory elements, to mention a few examples.
The easiest solution to heat fuses in conjunction with the phase change memory array is to permanently blow a phase change storage element. This can be done with high current pulses delivered to the phase change memory cell in reverse polarity.
Because it operates differently, the fuse array must include structural differences over the phase change memory elements. In particular, the reverse polarity and the high current for blowing fuses results in specific drivers and layout. As a result, the fabrication complexity may be increased by the inclusion of a fuse array on the same die with a memory array.